The thin film solar cell using CuInSe2 (CIS based thin film) which is the semiconductor thin film of chalcopyrite structure composed of a group Ib element, a group IIIb element, and a group IVb element, or Cu(In, Ga)Se2 (CIGS based thin film) which dissolves Ga to this, for an optical absorption layer, has an advantage that high energy conversion efficiency is indicated and there is little degradation of the efficiency according to light irradiation etc.
However, film formation by 550 degrees C. from a viewpoint of deterioration of film quality and increase of leakage current is general, in formation of the CIS based thin film which is the semiconductor thin film of chalcopyrite structure, or the CIGS based thin film which dissolves Ga to this. When it forms at low temperature rather than 550 degrees C., it has been considered that particle diameter is small composed and dark current characteristics deteriorate, conventionally. In addition, the heat-resistant limitation of an integrated circuit is about 400 degrees C.
On the other hand, a solid state imaging element characterized by forming a switching device by a thin film transistor on a substrate and laminating a sensor area by an amorphous semiconductor layer via a picture element electrode connected to the above-mentioned switching device or a solid state imaging element with which the above-mentioned substrate is formed by an insulating substrate is already disclosed (for example, refer to Patent Literature 1).
In the solid state imaging element disclosed in Patent Literature 1, since the amorphous semiconductor layer is made into a photo sensor area, a photoelectric conversion wavelength is mainly a visible light wavelength region.
Patent Literature 1: Japanese Patent Application Laying-Open Publishing No. 2001-144279
Currently, the CIS based thin film and the CIGS based thin film have the main use as a solar battery.
On the other hand, the inventors of the present invention have paid their attention to a high optical absorption coefficient of this compound semiconductor thin film material and characteristics with the high sensitivity which reaches the wide wavelength region from visible light to near infrared light wavelength region, and have examined using this compound semiconductor thin film material as an image sensor for a security camera (camera which performs sensing of the visible light at daytime and performs sensing of the near infrared light wavelength region at night), a personal authentication camera (camera for performing personal authentication with the near infrared light wavelength region which is not affected by an influence of outdoor daylight) or an in-vehicle camera (camera mounted in a car for visual aid at night, distant visual field securing, etc.).
An object of the present invention is to provide a solid state imaging device, with an easy structure, having the high sensitivity which reaches the wide wavelength region from visible light to near infrared light wavelength region and reducing dark current by providing a photoelectric conversion unit with a compound semiconductor film of the chalcopyrite structure composed of Cu(In, Ga)Se2 in the photoelectric conversion unit.
Moreover, an object of the present invention is to provide a fabrication method of the above-mentioned solid state imaging device.